Well having worked in several vet offices, I would personally not spay a cat unless I planned on giving her pain medicine. A spay is a very invasive and painful procedure. Neuters however do not involve going into the body and they experience very little pain. I would opt for the pain meds personally. But this is just my opinion. I have seen several cats given pain meds that still bounced around with no ill results. In fact all my females were active the next day. This shouldn't be a problem unless a cat starts licking the sutures or pulling on them. They will heal in the same amount of time whether they have pain meds or not.